Many years ago, bearings were often sealed by using a felt or similar sealing element positioned in contact with a rotary shaft and typically held in place by a metal shell. More recently, shaft bearings have mostly been sealed either with flexible lip seals or with labyrinth seals. However, each of these seals presents various operational problems. More specifically, lip seals have a finite and unpredictable life, they damage the surface on which the lip runs, they increase power consumption because of running torque, and they have limited temperature and speed capabilities. Drawbacks to labyrinth seals include an open path which does not totally prevent ingress of contaminants, a limited capacity to accommodate shaft misalignment and run out and an inability to handle fluid levels above the drain port or ports.
In prior labyrinth assemblies there have been instances in which excessive amounts of lubricant or other fluids have entered the labyrinth pathway in such volume that all of the fluid was unable to drain back into the internal cavity through the interior drain ports. In such instances, the excess fluid continues outwardly along the labyrinth pathway until it ultimately escapes from the exterior end of the labyrinth pathway or through an exterior drain port. In a somewhat similar manner, particulate contaminants of fluid and/or solid form have sometimes been able to pass inwardly along the labyrinth pathway to ultimately contaminate the internal cavity and its bearings.